(a) Field of the Invention
The present invention relates to a cellular phone, and a method and a program used in the cellular phone, and more specifically, an improvement of the receiving sensitivity for a radio frequency signal in the cellular phone.
(b) Description of the Related Art
A variety of clock frequencies are used in a cellular phone, such as shown in FIG. 12 showing a typical fold-type cellular phone. It is known in a general cellular phone that, if an integral multiple of a clock frequency used in the cellular phone coincides with the radio frequency, the receiving sensitivity for receiving the radio frequency signal is degraded in the radio channel using the radio frequency signal. It is also known that, if an integral multiple of one of frequency components in the transmission signal coincides with the radio frequency during transmission of data by using a data bus in the cellular phone, the receiving sensitivity for receiving the radio frequency signal is degraded.
FIG. 13 exemplarily shows the results of measurements of the receiving sensitivity of all the receiving channels in the cellular phone FIG. 13 is obtained for the case where a 10-MHz clock frequency is used as a synchronizing frequency of a data bus. As understood from the figure, the receiving sensitivity is significantly degraded at 81-, 82- and 83-times the 10-MHz synchronizing frequency of the data bus.
A fold-type cellular phone, such as shown in FIGS. 14A and 14B, having a top chassis section 201 mounting thereon a display unit 205 and a bottom chassis section 201 mounting thereon a keyboard (not shown) is increasingly used among the cellular phones having camera units thereon. The degradation of the receiving sensitivity is especially recognized for the case where a flexible printed circuit board 203 coupling together the top chassis 201 and the bottom chassis section 202 irradiates the 10 MHz synchronizing frequency as described above, and thus the antenna 204 of the cellular phone 200 receives the irradiated synchronizing frequency. It is to be noted that the camera unit may be provided on the top chassis section 201, although not specifically shown in FIGS. 12 and 13.
For example, in a typical cellular phone such as shown in FIG. 7, the control block 105 controlling the overall operation of the cellular phone includes a first clock generator 1051, a second clock generator 1052, PLL circuits 1053 and 1054. PLL circuit 1053 divides the system frequency of 14.4 MHz supplied from the first clock generator 1051 by four to generate a first system clock having a frequency of 3.6 MHz. The oscillation frequency of a voltage controlled oscillator 1055 receiving an output from PLL circuit 1053 is multiplied by fourteen and delivered to a CPU 1057 as a 50.4 MHz CPU clock after being synchronized with the 3.6 MHz first system clock.
PLL circuit 1054 divides the system frequency supplied from the first clock generator 1051 by four to generate a 3.6 MHz second system clock. The oscillation frequency of a voltage controlled oscillator 1056 is multiplied by ten and delivered to a DSP 1058 as a 36 MHz DSP clock after being synchronized with the 3.6 MHz second system clock.
Referring to FIG. 8 showing a display block (LCD block) 110 of the typical cellular phone, an LCD controller 1101-1 receiving the CPU clock 1201 from the control block 105 divides the CPU clock by five to deliver a data clock signal having a frequency of 10.08 MHz. Referring to FIG. 9 showing a camera block 114 of the typical cellular phone, a camera interface 1141-1 divides the CPU clock supplied from the control block 105 by six to deliver a data clock signal having a frequency of 8.4 MHz.
In the typical cellular phone, if a radio signal is received during operation of the LCD block 110, a degradation problem as to the receiving sensitivity occurs in the cellular phone. JP Patent Laid-open Publication 2000-184418 describes a technique for solving the above problem by delaying the output of the AC driving signal, horizontal scanning signal and frame signal in the LCD block until the receipt of the radio signal is completed, thereby suppressing noise caused by angle rotation of the LC molecules and thus suppressing degradation of the receiving sensitivity during the receipt of the radio signal.
In the described technique, however, there still occurs another degradation of the receiving sensitivity in the frequencies corresponding to integral multiples of the 3.6 MHz reference frequency, 10.08 MHz data clock frequency in the LCD block, and 8.4 MHz data clock frequency in the camera block.
In addition, data transmission through buses between the CPU and memory, between the CPU and LCD block, and between the CPU and camera block also degrades the receiving sensitivity in the cellular phone. Moreover, the described technique complicates the structures and control of the cellular phone.
The CPU disposed in the control block 105 operates for data processing at any time the data processing is requested. More specifically, if a data processing occurs, the CPU starts for the data processing, and stops after the completion of the data processing. In such a case, transmission of data through the data bus by the CPU may cause a significant degradation of the receiving sensitivity.
For example, in the processings shown in FIG. 10, when an interrupt signal is generated after completion of signal receipt, the CPU operates for processings A1 and A3, which do not cause any degradation of the receiving sensitivity because the processings A1 and A3 are out of the timing of the receiving slot. When another interrupt signal is generated after completion of a signal transmission, the CPU operates for processing A2, which does not cause any degradation of the receiving sensitivity because the processing A2 is out of the timing of the receiving slot.
When other interrupt signals are generated due to the operation on the man-machine interface, the CPU operates for data processings such as processings B1, B2 and B3, among which processings B1 and B3 may cause a degradation of the receiving sensitivity whereas processing B2 dose not cause any degradation. This is because the processings B1 and B3 are within the timing of the receiving slot and processing B2 is out of the timing of the receiving slot. The degradation of the receiving sensitivity caused by the processings B1 and B3 may be involved with the data transmission through the data bus during the CPU processings.
Further, as shown in FIG. 11, processings by the LCD block and the camera block may cause a degradation of the receiving sensitivity because these blocks operate for processings at random in asynchrony with the time division multiple access (TDMA) timing, and may fall within the timing of the receiving slot. In FIG. 11, camera control signal and camera data as well as the LCD control signal are delivered during the receiving slot. This may cause degradation of the receiving sensitivity.
It is an object of the present invention to provide a cellular phone, and a method and a program for suppressing a degradation of the receiving sensitivity in the cellular phone.
The present invention provides a cellular phone including: a radio circuit block including an antenna; an analog baseband block connected to the radio circuit block; a digital baseband block connected to the analog baseband block; and a control block for controlling operation of the blocks, the control block including a central processing unit (CPU) for treating data input from the blocks and the keyboard, the radio circuit block receiving a radio signal through the antenna during a receiving slot, wherein the control block stops operation of the CPU during the receiving slot.
The present invention also provides a cellular phone including: a radio circuit block including an antenna; an analog baseband block connected to the radio circuit block; a digital baseband block connected to the analog baseband block; at least one of display block and camera block, and a control block for controlling operation of the blocks, the control block including a central processing unit (CPU), the radio circuit block receiving a radio signal through the antenna during a receiving slot, wherein the at least one of display block and camera block stops data transmission through an associated bus during the receiving slot.
The present invention also provides a method for controlling a cellular phone having a CPU for controlling operation of the cellular phone and treating data in the cellular phone, the method including the step of: detecting a receiving slot to activate a receiving frame signal; retaining an interrupt signal during a time interval when the receiving frame signal is active; delivering the interrupt signal to the CPU after the receiving frame signal is inactivated; and operating the CPU for processing corresponding to the interrupt signal.
The present invention also provides a program stored in a medium for running on a CPU in a cellular phone, the program defining the steps of: detecting a receiving slot to activate a receiving frame signal; retaining an interrupt signal during a time interval when the receiving frame signal is active; delivering the interrupt signal to the CPU after the receiving frame signal is inactivated; and operating the CPU for processing corresponding to the interrupt signal.
In accordance with the cellular phone, method and program of the present invention, since at least one of operation of the CPU and transmission of data through the data bus is stopped during the receiving slot, the receiving sensitivity is not degraded in the receiving slot by the at least one of the operation of CPU and the transmission of the data.
The above and other objects, features and advantages of the present invention will be more apparent from the following description, referring to the accompanying drawings.